FIrewall with two internet lines

Hi all - Anybody has some info on where to start with a single firewall setup that has to filter internal traffic between two internet connections.
One connection will be used as the primary connection and will take care of all internet related activity EXCEPT for one specific traffic (ERP software). The ERP software should only be used for the second internet line.
In case the primary fails traffic should should then be redirected, either manually or automatically to the secondary and vice versa of course as well
At the moment I would be highly interested starting this with Linux - but if there is any hardware based solutions out there I would be defently all ears.

Is this by the way possible .... or am i just dreaming here ??

Is this by the way possible .... or am i just dreaming here ??

I'm (almost) certain it's possible, I just don't know how

www.linksys.com/products/product.asp?gri...scid=29&prid=639

This product will support up to 2 internet line.

www.linksys.com/products/product.asp?gri...scid=29&prid=624

This product will support up to 7 internet lines.